Process of extracting aromatic hydrocarbons



Jan. 31, 1950 A. P. LIEN Er AL 2,495,850

PRocEss oF EXTRACTING ARoMATIc HYDRocARBoNs Filed nec. 2v, 194e 2sheets-sheet 1 5E TTL [H Jrg Feed

i-N 4 4f my.

Jan 31, 1950 A. P. LIEN Er A1.

PROCESS 0F EXTRACTING AROMATIC HYDROCARBONS Filed nec. 2v, 194e 2Sheets-Sheet 2 ?aerrtecl Jan., Si, i195@ aaaassc PROCESS F EXTRCIINGROMTIC HYDRGCARBNS Arthur R Lien, Hammond, inail., and Bernard L,lEvering, Chicago, lill., assignors to Standard @il Company, Chicago,lill., a corporation ci indiana Application December 2'?, i946, SerialNo. 718,854

11 Claims.

This invention relates to the treatment of organic materials, and moreparticularly to the relining of organic materials containing mixtures ofhydrocarbons, such as aromatic, parafllnlc, naphthenic and/or olenichydrocarbons to selectively extract therefrom the aromatic hydrocarbons.It relates still more particularly to the selective extraction ofaromatic hydrocarbons from petroleum fractions containing the same.

The separation of aromatic hydrocarbons from parainic, naphthenic and/orolenic hydrocarbons in materials containing the same find application inmany fields. Among the many possible specific applications of theinvention are the treatment of petroleum cycle stocks to provide lessrefractory stocks for subsequent thermal or catalytic crackingoperations. Other specific applications will be readily apparent.

It is an object of the present invention to provide a method ofselectively separating aromatic hydrocarbons from paraflinic, naphthenicand/or oleilnic hydrocarbons in a mixture containing the same.

Still another object of the invention is to provide an improved methodof refining petroleum fractions to separate therefrom undesirablearomatic hydrocarbons.

A still further object of the invention is to provide an effectivemethod of refining hydrocarbons.

Other objects and advantages of the invention will become apparent fromthe following description thereof read in conjunction with theaccompanying drawings which form a part of the specification and inwhich Figure 1 is a flow-diagram of one method of carrying out theinvention, and

Figure 2 is a flow-diagram of a modied method of carrying out theinvention.

- In accordance with the present invention aromatic hydrocarbons areselectively separated from a mixture containing non-aromatichydrocarbons, such as parafilnic, naphthenic and/or olefinichydrocarbons by extracting such materials with a complex of boronfluoride (BFa) with an oxygenated organic compound, and the halogen,preferably chlorine, derivatives of such oxygenated organic compounds.The aromatic hydrocarbons and the non-aromatic hydrocarbons subjecttolseparation by the present invention may be normally liquid or liquidunder existing operating pressures. While complexes of BF: withaliphatic or aromatic or oxygenat'ed compounds can be used, we prefer toemploy complexes of BF; with an oxygenated alkane compound selected fromthe class consisting of ethers, esters and acids having not more thanabout 5,

Methyl ether Butyl formate Ethyl ether Ethyl propionate Propyl etherFormic acid Butyl ether Acetic acid Amyl ether Propionic acid PhenolAnisol Methylethyl ether Pyran Methyl acetate Tr- Ethyl acetate TetraPropyl acetate Penta- Amyl acetate methylene Methyl formate oxides Ethylformate and the halogenated, preferably chlorinated, derivatives of theabove as for example, B,B dichloroethyl ether (Chlorex) chloroaceticacid, etc.

While complexes of boron fluoride with oxygenated organic compounds as aclass are effective solvents for effecting a separation between aro-`matic hydrocarbons and paraiiinic, oleflnlc and/or naphthenichydrocarbons, they are all not equal in their eifectiveness andselectivity since the degree'of selectivity and effectiveness may varywith different complexes with the composition of the mixture beingextracted and with the conditions of extraction, as will be hereinafterdescribed.

The boron fluoride complexes are readily prepared by bubbling a slightmolar excess of boron fluoride through the oxygenated compound, e. g.ether, ester, acid, etc., and then subjecting the mixture to reducedpressure to remove the excess boron fluoride. In some cases, it isdesirable to carry out the BF; stripping step at lower than roomtemperature in order to avoid decomposition of the complex. The residualproduct is a complex of a mol to mol ratio of boron fluoride to theoxygenated organic compound. The complexes suitable for the hereindescribed inven.

tion are liquid or solids which melt slightly above room temperature, e.g. about F. to about F. A small amount, sufllcient to give a partialpressure of at least 15 pounds, and preferably from about 15 to 500pounds, per square inch, of boron fluoride may be used in conjunctionwith the herein described complexes, in order to effect increasedextraction, e. g. of higher molecular 55 weight aromatics.

The choice of anv particular organic oxygenated compounds used informing the boron iiuoride complex will depend upon the feed to betreated, with due consideration being given to the boiling point of thecomplex in relation to the boiling range of the feed material and theextract to be obtained therefrom. For example, the boron fluoride-methylether or boron fluorideethyl ether complexes boil at relatively lowtemperatures, namely 258 to 262 F. Therefore, if the extracted materialboils in this temperature range. it is preferable to use a higherboiling f complex. for example the adduct of boron fluoride with ahalogenated methyl ethyl ether. Of course, under some conditionscomplexes having a boiling point lower than that of the extractedmaterial may be used, in which case the complex can be recovered bydistilling or flashing off the same from the extract.

The extraction can be carried out over a wide temperature range. ofabout 50 F. to about 150 F. or higher, and preferably from about '10 F.to about 100 F. The quantity of complex used should be suilcient to givea diphasic separation and depending upon the material being extractedcan vary from 10 volume percent to about 200 volume percent or more,based on hydrocarbon feed, and preferably from about 50 volume percentto about 100 volume percent, although in some cases as little as 5volume percent or less will give a satisfactory diphasic separation. Apressure sufficient to keep the' materials in a liquid phase should bemaintained in the extractor. In the extraction of heavier stocks, suchas for example lubricating stocks or in separation of aromatics andolens, improved selectivity can be attained under certain conditions bythe addition to the extraction mixture of an inert paraiiin hydrocarbondiluent, such as for example pentane, hexane or heptane.

'Ihe following procedure of extracting a highly aromatic, relativelylow-boiling hydrocarbon feed stock with a boron fluoride-ethyl acetatecomplex is given by way of illustration only and is not intended to be alimitation of our invention. Referring to Figure l, a highly aromatic,low-boiling hydrocarbon feed stock is introduced through a line I intothe bottom portion of an extractor and countercurrently contacted with aboron fluoride-ethyl acetate complex introduced into the upper portionof the extractor I| through a line I2. The extractor I is suitably apacked column, although other known suitable means of obtaining intimatecontact can be employed. A raffinate is removed overhead from theextractor I through a line I3 and introduced into a settler Il whereinany carryover complex is settled out and returned to the extractor I Ithrough line |5. The raffinate, free of carryover complex, is withdrawnfrom the separator I4 through line I6 and introduced into the bottomportion of a still I1 provided with suitable heating means such asheating coil |8. The rannate substantially freed of aromatics is takenoif overhead through a line I9. The bottoms from the still |1 comprisinga boron fluoride-ethyl acetate complex is withdrawn from still I1through a line 20 and introduced into the complex storage tank 2|. Ifthe hydrocarbon feed stock distills above the boiling point of thecomplex, the aromatic-free raffinate is withdrawn as bottoms and thecomplex is taken overhead. Still I1 may be operated under reducedpressure.

The extract from the extractor is withdrawn therefrom through line 22and introduced into still 23 equipped with suitable heating means,

4 such as heating coil 2l. Still 23 may be operated at sub-atmosphericpressure. A fraction comprising substantially aromatic hydrocarbons isremoved overhead from still 23 through line 25,

5 while the complex, substantially free of aromatics, is withdrawnthrough line 26 and either introduced into the complex storage' tank 2|through line 21, or recycled to the extractor through line 28. VComplexfrom storage tank 2| is introduced into the extractor through lines 28,29 and I2. In order to supply make-up boron fluoride complex. boronfluoride is introduced into the storage tank 2| through line 30 andethyl acetate is added through line 3|. f

The foregoing example illustrates a method of carrying out the hereindescribed invention in which the boron fluoride complex is notdecomposed by distillation. However, certain boron .fluoride complexesare decomposed into boron fluoride and the oxygenated organic compoundwhen subjected to distillation, even vacuum distillation. When employingsuch complexes they cannot `be recovered as in the hereinbeforedescribed method. The following example illusz5 trates one method ofcarrying out the invention employing a boron fluoride complex which isdecomposable under distillation conditions. For ythe purpose ofillustration, the following procedure provides a method of carrying outthe invention employing as the solvent a boron fluoride-beta betadichloroethyl ether complex hereinafter referred to as the boronfluoride-Chlorex complex.

Referring to Figure 2, the feed to be extracted,

for example highly refractory aromatic cycle stock, is introducedthrough line ||0 into the bottom portion of extraction tower andcountercurrently contacted with a boron fluoride- Chlorex complexintroduced into the upper pornon of the tower In through une H2. Atemperature of about 40 to 90 F. is maintained in the extraction towerThe raffinate from the extraction tower III is removed overhead throughline |`l3 to a settler Ill, wherein any entrained boron fluoride-Chlorexcomplex is settled out and recycled to tower I through lines I I5 andIIB, or may be passed through lines ||5 and ||1 to a complex recoveryunit hereinafter described. The raffinate from the settler III is passedthrough o une Ha to a boron fluoride stripper H9 provided with suitableheating means such as a heating coil |20, wherein any small amount ofdissolved boron fluoride complex is decomposed by heating and the boronfluoride is removed overhead through lines |2| and |22 to a boronfluoride- Chlorex mixer |23. The bottoms from the stripper l I9 arewithdrawn through line |24 to a fractionator |25, provided with suitableheating o means such as a heating coil |26, wherein the Chlorex is takenoverhead through lines |21 and |28 to the boron fluoride-Chlorex mixer|23. 'I'he raffinate, freed of boron fluoride and Chlorex, is removedfrom the tower |25 through line |29. If

35 a light hydrocarbon diluent has been used it may be removed as anoverhead stream from the top of the fractionator |25 and the Chlorextaken off as a higher boiling side stream. Obviously, in the event thehydrocarbon product has a lower boiling point than the Chlorex, thehydrocarbon will be taken overhead from the fractionator |25 and theChlorex will be withdrawn from the fractionator |25 as a bottom andpassed to the boron ucride-Chlorex mixer.

The extract from the extractor tower comprising boron fluoride-Chlorexcomplex and the extracted material from the feed is removed from towerthrough line |30, and introduced into a stripper |3| provided withsuitable heating means such as heating coil |32 for maintaining a bottomtemperature of 180 F. to 400 F. in the stripper. Boron fluoride-Chlorexcomplex from the settler ||4 may be introduced into the stripper 13|through lines ||1 and |30. Boron fluoride is taken overhead through line|33 and passed via line |22 to the boron iluoride-Chlorex mixer |23.Bottoms from the stripper |3| are withdrawn through line |34 tofractionating tower |35, provided with suitable heating means such asheating coil |35, wherein the separation is made between the organicextracted* material and the Chlorex. Chlorex from the fractionator |35is taken overhead through line |37 and lntroduced via line |28 to theboron fluoride-Chlorex mixer |23. 'I'he extracted organic material iswithdrawn from the fractionating tower |35 through line |38.Alternately, the Chlorex may be withdrawn as bottom product if theboiling range of the extract is below the boiling point of Chlorex.

The boron uoride-Chlorex mixer is operated under cooling conditions toprevent excessive temperature due to the heat of reaction between theboron fluoride and Chlorex. Make-up boron fluoride is introduced t themixer through line |33 and the make-up Chlorex through line |40 insumcient quantity to maintain a stoichiometric ratio of the componentsof the complex. The boron uoride-Chlorex complex from mixer |23 isrecycled to the extraction tower through lines MI and ||2. Although theboron iluoride stripper and the Chlorex fractionator have been shown asseparate towers, a single tower may be used.

The applicability of boron uoride-complexes to the separation ofaromatics from paraffin hydrocarbons is demonstrated by the data inTable I below. 'I'he data presented therein were obtained in a one stepextraction of blends of 50% heptane and 50% benzene, ortho xylene, andmeta xylene with complexes of boron iluoride and various oxygenatedorganic compounds.

While the data in Table I are based on a single step extraction, animprovement can be obtained by carrying out the extraction in a numberof stages. This improvement'is illustrated by the data in Table II, inwhich a blend of 50% benzene and 50% heptane was extracted with boroniluoride-ethyl ether and boron uoride-propyl acetate complexes in oneand four stages, using a total of one volume of complex to one volumeoi' the hydrocarbon mixture in each case.

TABLE II One stage vs. four stage extraction o! 50% n-C1-50% CeHemixture Total Extraction, Complex Per Cent 1 stage' 4 Stage' Brr-EthylEther 54. 2 79. 1 BFf-Propyl Acetate 55. 6 77. 1

TABLE III One stage vs. four stages extraction of 50% cetane-50% CeHemixture 1 Stage 4 Stages The extraction of a polynuclear aromatic fromBF. Ethyl Ether TABLE I Selective extraction of aromatic-Parafia blendswith Bln-complexes 50% n-C1 50% n-01 60% n-C1 n-Heptane 50% CeHa 50%o-xylene 50% m-xylene Test Mix no* l. 3871 1.4301 1.4461 1. 4417Bry-Ethyl Acetate:

Ramnate np* 1.3871 1. 4128 1. 4342 1. 4319 Treating Loes, Vol. PerCent-..- 4 30 14 12 Per Cent Aromatics extracted l 50. 5 20. 2 17. 9selectivity factor 1. 5B 1. 44 BFa-Propyl Acetate:

Ramnate no 1. 3871 1. 4102 1. 4301 1. 4276 Treating Lou, Vol. Per Cent 555 30 36- Per Cent Aromatics extracted 1 55. 6 27. 2 25.8 selectivityfactor I l. 01 70 BFz-Acetlc Acid:

Rsnate nu 1.3871 1.4330 Treating Los, Vol. Per Cent 2 7 Per Cent Aromatiextracted l 11. 7 selectivity factor 1. 87 BFr-Ethyi Ether:

Ralnate np l. 3871 1. 4103 1. 42% 1. 4276 Treating Loss, Vol. Per Cent 558 4l 38 Per Cent Aromatics Extracted 1 54. 2 27. 6 25. 8 selectivityFactor l 93 67 BFa-Anisole:

Railinate no 1. 3m 1. B40 L 4437 1. 4387 Treating Loss, Vol. Per Cent 386 55 51 Per Cent Aromatics extracted l 8. 1 4. 1 5. 5 selectivityfactor L--- 12 0. 07

Baeedonn i n i l selectivity lector-aromatica extracted divided bytreating lose; perfect selectivity equals 2. 0.

guasto a mixture containing polynuclear aromatica and non-aromatichydrocarbons is demonstrated by the data in Table IV, in which a mixtureof 20% anthracene oil and 80% heptane was extracted with an equal volumeoi' boron fluoride-ethyl ether complex in one stage.

TABLE IV con. heptane-aber, antnncene 011 n 1.4326 mante no 1.4083Aromatic extracted based on nl,o n

per cent.- 53.4 Treating loss -do Aromatic based on treating loss -do.--50 The foregoing data demonstrate the eil'ectiveness o! complexes ofboron iluoride and an oxygenated organic compound in extractingpolynuclear aromatic hydrocarbons from a mixture containing paraillnic,naphthenic and/cr. oleilnic hydrocarbons The degree of extraction to beobtained with a complex mixture of higher molecular weight aromatica,parafllns, naphthenes and oleilns is demonstrated in Table V 4by anumber of experlments carried out on a sample of highly refractory gasoil cycle stock, obtained by multiple recycling of East Texas naphthenicgas oil in a catalytic cracking process.

- TABLE V of cycle stock and BF: ethyl ether complex. Comparison of thisrun with run 6 shows that aromatic extraction is markedly increased overthat obtained with RF1. ethyl ether complex in the absence of excess BF:and this without attendant loss in selectivity. The results in run 'Iindeed approach closely those obtained with the relatively highlydissociated BFa. Chlorex cornplex (run 8). Although the presence of freeBF: increases' the degree of extraction when used in conjunction with aBF: oxygen complex, it is seen from run 1 that BF: alone has littleeiect in aromatic removal.

The effect of multiple stage contacting is shown by run 11. In this casea given sample of the cycle stock was contacted with equal volumes offresh BFaethyl ether complex in 4 successive treats. Examination of thephysical properties o! the ilnal rainate shows it to be less aromaticExtraction of cycle stock from East Texas naphthenic gas oil (one volumeBF: complex volume oil) i Ramnate Run No. man; Agent V'lfgef'tselectivity l no* D4 Gas 011 l- {Bycie Stock... "mm-"i5 ""mmil 1. 13 16.6 23 16. 4

14.1 16.3 30 16. BF1.Propyl Ether- 45 12.4 BFLADISOIG 33 15. 0 BF1.Ethy1Ether, 4-Stage l. 0. 840 38 l0. 0

l selectivity-ratio no* divided by treating lossXlO.

The measure of selectivity in the above experiments is shown as theratio of index change to treating loss. It is seen that most of thecomplexes show about the same degree of selectivity, in direct contrastto the results on the lower moiecular weight aromatics as shown in TableI. Thus, anisole which is entirely unsatisfactory for extraction ofbenzene or xylene because of extremely poor selectivity (Table I),effects a high degree of extraction of aromatica from cycle stock with agood selectivity.

In the case of aromatics in the gas oil range, the degree of extractionincreases markedly with increase in molecular weight of the organicportion of the BF: complex. Thus with the ethers (ROR), there is adennite progression as R is changed from methylto ethylto propyl. Thesame eilect is noted in comparing the esters.

These eil'ects, holding only for the higher mocomplexes of boronfluoride and oxygenated compounds of the type herein described areeffective in removing organic sulfur compounds, and colorforming bodiesfrom organic materials, particularly hydrocarbons.

While we have described our invention with reference to certain specificembodiments thereof, the invention is not to be considered limitedthereto, but includes within its scope such modifications as come withinthe appended claims.

We claim:

1. The method of extracting aromatic hydrocarbons from a mixturecomprising normally lic| uid aromatic hydrocarbons and normally liquidnon-aromatic hydrocarbons, comprising extracting said mixture at atemperature `within the range of from about 50 F. to about 150 F. with acomplex of boron uoride with an oxygenated organic compound insuillcient quantity to form a diphasic separation, separating a fractioncomprising essentially said non-aromatic hydrocarbons and a minor amountof said complex, and

a fraction comprising essentially aromatic hydrocarbons dissolved insaid complex, and separating said complex from said fractions.

2. The method of extracting aromatic hydroing said mixture at atemperature within the range of from about 50 F. to about 150o F. with acomplex of boron fluoride with an oxygenated alkane compound having notmore than about carbon atoms in the alkyl group, in suilicient quantityto form a diphasic separation, separating a fraction comprisingessentially said nonaromatic hydrocarbons and a minor amount of saidcomplex, and a fraction comprising essenltially aromatic hydrocarbonsdissolved in said complex. v

3. The method described in claim 2 in which the oxygenated alkanecompound is an alkane ester. l

4. The method described in claim 3 in which the alkane ester is ethylacetate.

5. The method described in claim 2 in which the oxygenated alkanecompound is an alkane ether.

6. The method described in 'claim 5 in vvhich the alkane ether is anethyl ether.

7. The method described in claim 6 in which the alkane ether is beta,beta dichloroethyl ether.

uid aromatic hydrocarbons and normallyliquid non-aromatic hydrocarbons,comprising contacting said mixture at a. temperature within the range offrom about 50 F. to about 150 F. with a complex of boron uoride and anoxygenated organic compound in suilicient quantity to form a diphasicseparation,'separating a raiinate fraction comprising essentiallynon-aromatic 'hydrocarbons and a minor amount of said complex and anextract fraction comprising essentiallyl aromatic hydrocarbons dissolvedin said complex and separating said complex from the railinate andextract fraction. l

l11. The method of extracting high molecular weight polycyclic aromatichydrocarbons from a mixture comprising normally liquid high molecularweight polycyclic aromatic hydrocarbons and normally liquid non-aromatichydrocarbons, comprising contacting said mixture at a temperature withintherange of from about 50 F. to

about 150 AF. with a solventi comprisingessen- 81 The method describedin claim 2 in which I the oxygenated alkane is an alkane acid.

9. The method of extracting aromatic hydrocarbons from a mixturecomprising aromatic hydrocarbons and parailinic hydrocarbons comprisingextracting said mixture at a temperature within the range of from about50 F. to about 150YF. with a complex of boron fluoride with anoxygenated alkane compound having not more than about 5 carbon atoms inthe alkyl group in 'suicient quantity to form a diphasic separation,separating a rafdnate comprising vessentially paraillnic hydrocarbonsand said complex and an xtract comprising essentially aromatichydrocarbons, and said complex, and separating said complex from theraillnate and extract fractions.

10. The method of extracting aromatic hydrocarbons from a mixturecomprising normally liqtially a complex of boron uoride with anoxygenated organic compound, and an excess of boron fluoride suilcientto give` a partial pressure of at least 15 pounds per square inch,separating a raffinate comprising essentially non-aromatic hydrocarbonsand a small amount of said solvent and an extract comprising essentiallyaromatic hydrocarbons and said solvent, and separating said solvent fromsaid raffinate and extract.

ARTHURP. LIEN. BERNARD lL. EVERING.

REFERENCES CITED The following references are of'record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,246,257 .Kohn June 17, 19412,257,086 A'twell Sept. 30, 1941 2,260,279 D'Ouville et al Oct. 21, 19412,343,744l Burk Mar. 7, 1944 2,415,171 Horeczy Feb. 4. 19.47

2. THE METHOD OF EXTRACTING AROMATIC HYDROCARBONS FROM A MIXTURECOMPRISING NORMALLY LIQUID AROMATIC HYDROCARBONS AND NORMALLY LIQUIDNON-AROMATIC HYDROCARBONS, COMPRISING EXTRACTING SAID MIXTURE AT ATEMPERATURE WITHIN THE RANGE OF FROM ABOUT 50*F. TO ABOUT 150*F. WITH ACOMPLEX OF BORON FLUORIDE WITH AN OXYGENATED ALKANE COMPOUND HAVING NOTMORE THAN ABOUT 5 CARBON ATOMS IN THE ALKYL GROUP, IN SUFFICIENTQUANTITY TO FORM A DIPHASIC SEPARATION, SEPARATING A FRACTION COMPRISINGESSENTIALLY SAID NONAROMATIC HYDROCARBONS AND A MINOR AMOUNT OF SAIDCOMPLEX, AND A FRACTION COMPRISING ESSENTIALLY AROMATIC HYDROCARBONSDISSOLVED IN SAID COMPLEX.